Compensating sheave apparatus for elevators

ABSTRACT

Compensating sheave apparatus for an elevator system having an elevator car, a counterweight, a hoisting machine, hoisting roping and compensating roping, wherein the compensating sheave apparatus includes a tensioning sheave for said compensating roping, a weight frame for said tensioning sheave, fixed guide rails for guiding the weight frame, and a safety device for coupling the weight frame to the guide rails only when the safety device is upwardly accelerated at a predetermined acceleration rate by the weight frame, and wherein the safety device includes coupling members, operative to grip the guide rails when the coupling members are actuated, and an inertial actuator having an inertial mass, operative to actuate the coupling means when the inertial mass senses the predetermined acceleration rate.

United States Patent Showalter [451 Apr. 4, 1972 [72] Inventor: JohnMelville Showalter, Clark, NJ.

[73] Assignee: Otis Elevator Company, New York, N.Y.

[22] Filed: Jan. 21, 1969 [2]] Appl. No.: 792,352

[52] U.S.Cl ..187/22, 187/89 [51] Int. Cl ..B66b 11/04 [58] FleldofSearch ..187/38, 39,22, 89-91; 188/188 [56] References Cited UNITEDSTATES PATENTS 1,789,008 1/1931 Lindquist ..187/89 2,142,354 l/1939Harper ..187/38 2,244,893 1/1941 Panter ..187/73 2,490,653 12/1949Sah1in.... ....187/90 3,346,073 10/1967 Martin ....l87/90 1,953,1194/1934 McCormick ..187/22 FOREIGN PATENTS OR APPLICATIONS 1,558,0903/1968 France ..187/89 Primary Examinerl-larvey C. Hornsby AnorneyJosephL. Sharon and Thomas W. Kennedy 57 ABSTRACT Compensating sheaveapparatus for an elevator system having an elevator car, acounterweight, a hoisting machine, hoisting roping and compensatingroping, wherein the compensating sheave apparatus includes a tensioningsheave for said compensating roping, a weight frame for said tensioningsheave, fixed guide rails for guiding the weight frame, and a safetydevice for coupling the weight frame to the guide rails only when thesafety device is upwardly accelerated at a predetermined accelerationrate by the weight frame, and wherein the safety device includescoupling members, operative to grip the guide rails when the couplingmembers are actuated, and an inertial actuator having an inertial mass,operative to actuate the coupling means when the inertial mass sensesthe predetermined acceleration rate.

13 Claims, 8 Drawing Figures Patented April 4, 1972 2 Shoots-Sheet l BYWmw 11/, KW ATTORNEY Pat ent ed April 4, 1972 ulLlllllT LWME V Y/ 2shuts-shat 2 INVENTOR JOHN MELVILLE SHOWALTER COMPENSATING SHEAVEAPPARATUS FOR ELEVATORS The present invention relates to elevatorsystems, and particularly to an elevator system having a compensatingrope sheave.

A conventional elevator system includes an elevator car, acounterweight, and a plurality of hoisting ropes, which suspend theelevator car and counterweight. The hoisting ropes pass over a hoistingsheave, which is disposed at the top of the hatchway. The elevatorsystem also includes compensating ropes, which are suspended from theunderside of the elevator car and counterweight in order to compensatefor the unbalanced weight of the hoisting ropes. The compensating ropeshave a compensating sheave unit, which is disposed at the bottom of thehatchway for guiding and tensioning the compensating ropes.

A conventional compensating sheave unit includes a compensating sheave,which guides the compensating ropes, a weight frame, which is connectedto the sheave, a pair of fixed guide rails, which guide the weightframe, a safety block, which is connected to the weight frame, and aplurality of braking members, which are disposed between the safetyblock and the pair of guide rails. A conventional compensating sheaveunit of this type is described in U.S. Pat. No. 1,789,008, issued Jan.13,1931.

The conventional compensating sheave unit ties down the compensatingropes and assures that the car, counterweight and ropes function as aclosed system. In this way, deceleration forces, which are applied tothe system, act on the total mass of the system. In addition, impactforce, which the counterweight applies to the hoisting ropes and whichis caused by the sudden rise and fall of the counterweight when thedescending car is suddenly decelerated, is minimized.

The conventional compensating sheave unit also has a pair of coilsprings, which are disposed between the safety block and the weightframe. These springs permit a limited upward movement of the weightframe relative to the safety block when the safety block grips the guiderails. This movement takes care of some of the longitudinal shrinkage inthe hoisting and compensating ropes caused by changes in the temperatureand humidity. However, in some elevator installations, the limitedmovement permitted by the coil springs is insufficient to take care ofall of the rope shrinkage so that the rope stress is increased. Forexample, in a high-rise elevator installation in an air-conditionedbuilding, if the air conditioning is shut off over a weekend, arelatively large increase in humidity can occur. This causes the ropesto swell in diameter thereby causing a substantial rope shrinkage inlength and resulting rope stress.

In accordance with one embodiment of the present invention, rope stressdue to such rope shrinkage is eliminated by providing a safety apparatusincluding a safety block, which is connected to the weight frame,braking members, which are mounted on the safety block for engaging theguide rails, and an inertial actuator, which is mounted on the safetyblock, and which senses an acceleration force applied thereto, and whichapplies the braking members to the guide rails only upon sensing apredetermined acceleration force. In this way, when the compensatingropes exert a predetermined acceleration force upon the sheave unit, thebraking members are applied, but when the compensating ropes exert arope shrinkage force on the sheave unit, or an acceleration force lessthan the predetermined acceleration force thereon, the braking membersare not applied. Thus, the compensating sheave unit can move up or downwithout restraint to follow the rope shrinking and rope expansion. Also,the compensating sheave unit can grip the guide rails in order to tiedown the compensating ropes when the elevator car is decelerated at apredetermined deceleration rate so as to assure that the car,counterweight and ropes function as a closed system.

Accordingly, it is one object of the invention to provide an elevatorsystem having a compensating rope sheave unit, wherein rope stresscaused by rope shrinkage is minimized.

It is another object of the invention to provide an elevator systemaccording to the aforementioned object wherein the compensating sheaveunit is actuated to fixedly tie down the compensating ropes only whenthe compensating ropes apply a predetermined acceleration force to thecompensating sheave unit.

It is a further object of the invention to provide an elevator systemaccording to the aforementioned objects wherein the compensating sheaveunit includes a sheave frame, a separate safety brake apparatusconnected to the sheave frame, and a separate inertial actuator that isoperative to actuate the safety brake apparatus only upon sensing apredetermined acceleration force.

It is still another object of the invention to provide an elevatorsystem according to the aforementioned objects wherein the compensatingsheave unit includes adjusting means for changing the level of thepredetermined acceleration force at which the safety brake apparatus isactuated.

According to the present invention, there is provided an elevatorsystem, comprising, an elevator car, a counterweight, a hoistingmachine, hoisting roping, compensating roping, a tensioning sheave forsaid compensating roping, a weight frame connected to said tensioningsheave, guide rail means for guiding said weight frame, a safety blockconnected to said weight frame and cooperating with said guide railmeans, coupling means mounted on said safety block and movable relativethereto, said coupling means being operative to grip said guide railmeans when said coupling means is actuated, and an inertial actuatormounted on said safety block, said inertial actuator having an inertialmass, said inertial mass being movable relative to said safety block forsensing the acceleration rate of said safety block, said inertialactuator being operative to actuate said coupling means when saidinertial mass senses a predetermined acceleration rate.

Other objects of the invention will become apparent upon reading thefollowing description and accompanying drawings, wherein like parts aredesignated by like numerals throughout the several views, and wherein:

FIG. 1 is a schematic elevation view of an elevator system having acompensating rope sheave unit embodying features of the presentinvention;

FIG. 2 is an enlarged portion of FIG, 1;

FIG. 3 is a sectional view as taken along the line 3-3 of FIG. 2;

FIG. 4 is a sectional view as taken along the line 4-4 of FIG. 3;

FIG. 5 is a sectional view as taken along the line 55 of FIG. 4;

FIG. 6 is a sectional view as taken along the line 6-6 of FIG. 5;

FIG. 7 is a sectional view as taken along the line 77 of FIG. 5; and

FIG. 8 is a sectional view as taken along the line 8-8 of FIG. 5.

Referring to FIG. 1, one embodiment of the present invention is anelevator system 10. Elevator system 10 includes an elevator car 11, anda counterweight 12 for car 11. System 10 also includes an elevatorhoisting machine sheave 13, a deflector sheave l4, and a plurality ofhoisting ropes 15, which support car 11 and counterweight 12. System 10also includes a plurality of compensating ropes 16, which connect to car11 and counterweight l2, and a compensating sheave assembly 17, whichguides compensating ropes l6.

Hoisting ropes l5 and compensating ropes 16 are connected to car 11 andcounterweight 12 so as to form a continu' ous closed loop, which issupported by hoisting machine sheave 13. Compensating ropes 16compensate for the unequal distribution of weight of the hoisting ropes15 due to the movement of car 11 and counterweight 12. The total weightof the loop of ropes 15, 16 at any position of car 11 and counterweight12 is distributed in approximately equal amounts on each side ofhoisting machine sheave 13. Thus, the tractive effort of hoistingmachine sheave 13 on hoisting ropes 15 is improved. In addition,compensating sheave assembly 17 is positioned within the bottom loopportion of compensating ropes 16 in order to guide and tension ropes 15,16 and in order to cause car 11, counterweight 12 and ropes 15, 16 toact as a unit mass during deceleration of car 11, as explainedhereafter.

Sheave assembly 17 includes a compensating sheave 20, which guidescompensating ropes 16, a weight frame 21, which is connected tocompensating sheave 20, a pair of guide rails 22, 23, which guide frame21, and a safety apparatus 24, which fixedly couples and secures frame21 to guide rails 22, 23 when the upward acceleration rate of the safetyapparatus 24 exceeds a predetermined rate of acceleration.

counterweight l2 normally applies an upward acceleration force throughcompensating ropes 16 to sheave assembly 17 when car 11 is deceleratedduring downward movement of car 11. When sheave assembly 17 is upwardlyaccelerated by such force at a predetermined acceleration rate, sheaveassembly 17 automatically grips rails 22, 23 as explained hereafter. Inthis way, the upward movement of sheave assembly 17 is minimized, andcar 11, counterweight l2, hoisting ropes and compensating ropes l6decelerate substantially as a unit mass. In addition, the upwardmovement and subsequent unrestrained, downward fall of counterweight 12is minimized, so that stresses in hoisting ropes 15 are minimized.

In addition, when humidity and temperature changes cause a longitudinalshrinkage in ropes 15, 16, the rope shrinkage forces resultingtherefrom, which have substantially no acceleration rate, are relievedby an upward movement of sheave assembly 17 relative to rails 22, 23.Thus, stresses in ropes 15, 16 caused by rope shrinkage forces are alsominimized.

Compensating sheave 20 is journaled on a shaft 25, which is fixedlyconnected at the ends thereof to frame 21. Frame 21 is guided by rails22, 23 for vertical movement of frame 21 relative to the rails. Sheave20 is supported by frame 21 for rotation of sheave 20 relative to frame21. In this way, compensating ropes 16 are guided by sheave 20 as car 11and counterweight 12 move relative to each other. In addition, becausesheave 20 is carried by ropes 16 and frame 21 is carried by sheave 20,the weight of frame 21 and sheave 20 act to tension ropes 16.

Frame 21 includes a pair of wall members 30, 31, which are connectedtogether by bolt connectors 32, or the like. Wall members 30, 31 aresymmetrically disposed about an assembly joint 33, and are journaled onshaft 25, and are disposed on opposite sides of sheave 20. Wall 30 has apair of parallel guide bars 34, 35, which are fixedly connected theretoand which receive guide rail 22 therebetween. Wall 31 also has acorresponding pair of parallel guide bars 36, 37, which are fixedlyconnected thereto and which receive guide rail 23 therebetween.

Guide rails 22, 23 are fixedly connected at the lower ends thereof torespective support members 38, 39, which rigidly support guide rails 22,23. Rail 22 (FIG. 4) has opposite bearing surfaces 40, 41 for guidingbars 34, 35; and rail 23 has similar opposite bearing surfaces 42, 43for guiding its bars 36,

Safety apparatus 24 includes a crosshead or block assembly 44, which isdisposed between rails 22, 23, and includes a pair of braking members45, 46, which clamp and secure block assembly 44 to rails 22, 23 whenactuated. Apparatus 24 also includes an inertial actuator 47, whichactuates braking members 45, 46 only when block assembly 44 is upwardlyaccelerated at the predetermined acceleration rate by the accelerationforce from compensating ropes 16.

Block assembly 44 includes a pair of end block portions 49, 50, and apair of cover plates 51, 52. Plates 51, 52 are connected to blockportions 49, 50 by respective connector bolts 53, 54 for ease ofassembly. Cover plates 51, 52 respectively have adjacent end slots 55,56 on one side thereof, which receive rail 22, and adjacent end slots57, 58 on the other side thereof, which receive rail 23 for guidingblock assembly 44 along rails 22, 23.

Block assembly 44 has a pair of studs 59, 60, which are fixedlyconnected at the bottom ends thereof to frame 21 and which are slidablyconnected to block assembly 44. Studs 59,

60 guide frame 21 for movement of frame 21 relative to block assembly44. Studs 59, 60 have respective compression springs 61, 62, which areconcentric therewith. Studs 59, 60 respectively extend through bottomaperture 63 and top apertures 65, 66, which are disposed in cover plates51, 52. Studs 59, 60 are fixedly connected at the lower ends thereof toa lower stop plate 67, which is also fixedly connected to frame 21; andstuds 59, 60 are connected at the upper ends thereof to an upper stopplate 68, which limits the amount of movement of frame 21 relative toblock assembly 44. Springs 61, 62 respectively extend through apertures63, 65, and extend between cover plate 52 and stop plate 67. With thisconstruction of block assembly 44, the movement of frame 21 relative toblock assembly 44 is guided by studs 59, 60, and the extent of movementof frame 21 toward block assembly 44 is limited by lower stop plate 67,and the extent of movement of frame 21 away from block assembly 44 islimited by upper stop plate 68.

Springs 61, 62, which are alike, preferably have a high enough totalspring rate to transmit the predetermined acceleration force from frame21 to block assembly 44 immediately before block assembly 44 is clampedto rails 22, 23 by braking members 45, 46. Springs 61, 62 alsopreferably have a low enough spring rate to be compressed sufficientlyby the predetermined acceleration force to permit frame 21 to contactblock assembly 44 immediately after block assembly 44 is clamped torails 22, 23 by braking members 45,46.

End block 49 has an outer face 69, which has a recess that receivesguide rail 22. Recess 70 has oppositely facing sidewalls 71, 72, whichare disposed on opposite sides of guide rail 22. Sidewall 71 has avertical surface 73, which is disposed substantially parallel to itsadjacent rail surface 40. Sidewall 72 has an inclined cam surface 74,which is inclined relative to its adjacent rail surface 41. Cam surface74 cooperates with braking member 45 to lock end block 49 to rail 22 asexplained hereafter.

Sidewall 71 supports a bearing plate 75, which is disposed between railsurface 40 and sidewall surface 73. Sidewall 71 also has an aperture 76,which has a pin 77 disposed therein that engages plate 75. Aperture 76also has a compression spring 78 disposed therein, which engages pin 77so that spring 78 urges pin 77 against plate 75. In this way, plate isurged against rail surface 40 and the edges of end slots 55, 56 areurged against the opposite rail surface 41 for positioning and aligningend block 49 relative to rail 22. Sidewall 71 also has a spring retainerplate 79 bolted thereto, which closes one end of aperture 76. Plate 75guides and supports pin 77 and retains spring 78 in aperture 76; andplate 75 is removable for ease of installation of spring 78.

End block 50 also has a corresponding outer face 80, which has a recess81 that receives guide rail 23. Recess 81 also has opposite sidewalls82, 83. Sidewall 82 has an inclined cam surface 84, and sidewall 83 hasa vertical surface 85. Sidewall 83 has a bearing plate 86, which engagesrail surface 43, and has an aperture 87, which receives a pin 88 thatengages plate 86. Aperture 87 has a compression spring 89 that engagespin 88 urging pin 88 against plate 86 and urging plate 86 against railsurface 43. Sidewall 83 also has a removable spring retainer plate 90closing one end of aperture 87. Springs 78, 89, which are alike,preferably have a nominal spring rate, which is high enough to assurethat plates 75, 86 continually engage rails 22, 23 whereby noise causedby repetitive contact between block assembly 44 and rails 22, 23 isminimized. Springs 78, 79 provide a nominal friction between blockassembly 44 and rails 22, 23, and studs 59, 60 allow some movement offrame 21 relative to block assembly 44, so that frame 21 can move up ordown relative to block assembly 44 for a nominal distance without movingblock assembly 44.

Braking members 45, 46, which are rollers, are respectively disposedadjacent to cam and rail surfaces 74, 41 and 84, 42,

for coupling rails 22, 23 to end blocks 49, 50. Rollers 45, 46respectively bear against their adjacent rail surfaces 41, 42 and arenormally separated, when not actuated, from their adjacent cam surfaces74, 84 by respective gaps 91, 92. When rollers 45, 46 are actuated atthe predetermined acceleration, rollers 45, 46 are simultaneously urgedby actuator 47 to engage respective cam surfaces 74, 84. Such engagementcauses rollers 45, 46 to become wedged between their adjacent surfaces74, 41 and 84, 42. A slight upward movement of end blocks 49, 50relative to rails 22, 23, which occurs simultaneously therewith, causesrollers 45, 46 to become tightly wedged between surfaces 74, 41 and 84,42. In this way, block assembly 44 is rigidly coupled and secured torails 22, 23 by rollers 45, 46. In addition, when rollers 45, 46 bearagainst respective rails 22, 23 on one side thereof, plates 75, 86 bearagainst respective rails 22, 23 on the exact opposite side thereof sothat eccentric forces and moments on rails 22, 23 and on end blockportions 49, 50 are avoided.

Actuator 47 includes a torque shaft 100, which interconnects rollers 45,46 for simultaneous movement thereof, an inertial mass 101, which iseccentrically connected to torque shaft 100 for simultaneously actuatingrollers 45, 46, and a restraining mechanism 102, which selectively lockstorque shaft 100 for restraining inertial mass 101 from actuating therollers 45, 46, except when block assembly 44 is accelerated at thepredetermined acceleration rate.

Shaft 100, which has an axis of rotation 103, includes an integralradial arm 104, which is disposed near the middle of shaft 100 and whichis fixedly connected to inertial mass 101 for angular displacement ofmass 101 about axis 103. Shaft 100 also includes a pair of integralradial arms 105, 106, which are disposed near the axially outer endsthereof and which are respectively connected to a pair of links 107,108. Links 107, 108 are pivotally connected at their radially inner endsto arms 105, 106 and are fixedly connected at their radially outer endsto respective roller pins 109, 110. Pins 109, 110, which aresubstantially parallel to axis 103, are respectively journaled inrollers 45, 46 for rotary movement of rollers 45, 46 about pins 109, 110when rollers 45, 46 roll on rail surfaces 41, 42. Arms 105, 106 extendradially outwardly from shaft axis 103, and links 107, 108 extendradially outwardly from end arms 105, 106 for angular displacement ofrollers 45, 46 about axis 103 when actuated by shaft 100. In this way,inertial mass 101 and rollers 45,46 are eccentrically connected to shaft100 for simultaneous transfer of force and simultaneous engagement ofrollers 45, 46. Thus, when inertial mass 101 is angularly displacedabout axis 103 relative to block assembly 44 at the predeterminedacceleration rate, the acceleration force acting upon inertial mass 101is simultaneously transferred to rollers 45, 46. In addition, rollers45, 46 simultaneously engage cam surfaces 74, 84, so that sloping ortilting of block assembly 44 relative to rails 22, 23 is minimized.

Shaft 100 is mounted on a pair of support bars 111, 112, which arefixedly connected to cover plates 51, 52. Bars 111, 112, which arespaced apart, have respective bearings 113, 114, in which shaft 100 isjournaled for rotation of shaft 100 relative to block assembly 44.

With this construction, inertial mass 101 can apply upon shaft 100 anactuating torque, which is proportional in amount to the amount of thepredetermined acceleration rate applied to block assembly 44.Restraining means 102 can also apply upon shaft 100 a restrainingtorque, which acts counter to the actuating torque and which issubstantially constant in amount, as explained hereafter. When blockassembly 44 is accelerated at the predetermined acceleration rate, theactuating torque corresponding thereto, which exceeds the restrainingtorque, causes shaft 100 to rotate. When shaft 100 rotates, inertialmass 101 then applies its actuating torque upon rollers 45, 46 urgingrollers 45, 46 against cam surfaces 74, 84. At the same time, the slightupward movement of block assembly 44 causes rollers 45, 46 to becometightly wedged between surfaces 73, 74 and 84, 85. In this way, blockassembly 44 is secured to guide rails 22, 23 when block assembly 44 isupwardly accelerated at the predetermined acceleration rate.

Restraining mechanism 102, which is a latching type of device, includesa catch bar 120, which is fixedly connected to shaft 100, and a latchpin 121, which is received in a cylinder 122 that is fixedly connectedto support bar 1 11.

Latch pin 121, which is slidably received within cylinder 122 for axialdisplacement relative thereto, has an enlarged head portion 123 at oneend thereof having a pointed tip por tion 124, which projects fromcylinder 122 and which engages a notch 125 in catch bar 120. Latch pin121 also has an elongate shank portion 126, which projects from theother end of cylinder 122 and which has an assembly nut 127 threadedthereon for ease of assembly of latch pin 121 and cylinder 122.

Cylinder 122, which is a hollow member that has internal threads,receives an adjusting screw 128 forming the end wall thereof. Cylinder122 also receives a compression spring 129, which is disposed betweenadjusting screw 128 and head portion 123 for urging latch pin 121 in anyaxially outward direction. Adjusting screw 128 is axially adjustablerelative to cylinder 122 for adjusting the spring rate of spring 129.Ad-

' justing screw 128, which has an aperture 130 at the center thereofthat receives shank portion 126, is disposed between spring 129 andassembly nut 127 for guiding the movement of latch pin 121.

With this construction, when tip portion 124 is received in notch 125and bears against catch bar 120, assembly nut 127 on latch pin 121 isaxially displaced from adjusting screw 128, so that spring 129 appliesits axial spring force through tip portion 124 to catch bar 120.However, when tip portion 124 is not received in notch 125 and does notengage catch bar 120, assembly nut 127 bears against adjusting screw 128so that spring 129 applies its axial spring force upon adjusting screw128.

When tip portion 124 is received in notch 125 and when inertial mass 101applies its actuating torque on shaft 100, notch 125 applies atransverse force against tip portion 124. Spring 129 exerts against tipportion 124 an axial force, which is proportional to the spring rate.Tip portion 124 exerts a transverse reaction force against notch 125that causes a restraining torque on shaft 100, When the actuating torqueexceeds the restraining torque, and the actuating force upon latch pin121 exceeds the reaction force therefrom, spring 129 is com pressed andlatch pin 121 is deflected inwardly. As latch pin 121 is deflectedinwardly, shaft and catch bar rotate, catch bar 120 is disengaged fromlatch pin 121, and the restraining torque on shaft 100 ceases. Theactuating torque is thereafter directly transmitted from inertial mass101 through shaft 100 to rollers 45, 46. In this way, restrainingmechanism 102 releases rollers 45, 46 when the predeterminedacceleration rate is applied to safety apparatus 24. In addition,restraining mechanism 102 can be adjusted by turning screw 128 in orderto change the level of the predetermined ac celeration rate at whichshaft 100 and rollers 45, 46 are released.

Apparatus 24 also has a switch device 131. Switch 131 includes a bodyportion 132, which is fixedly mounted on block assembly 44, and aspring-biased tripper pin 133, which is slidably mounted on blockassembly 44 for movement of tripper pin 133 relative to body portion 132for actuating body portion 132. Tripper pin 133 has an end portion 134,which is disposed between block assembly 44 and weight frame 21. Endportion 134 is arranged to engage weight frame 21, and to thereuponactuate body portion 132, only when weight frame 21 engages blockassembly 44.

Switch 131 is actuated only when the predetermined acceleration forcedisplaces inertial mass 101 relative to block assembly 44 therebyclamping rollers 45, 46 to rails 22, 23, and only when the predeterminedacceleration force continues for a long enough time interval so thatframe 21 compresses springs 61, 62 and engages block assembly 44 therebyactuating switch tripper pin 133. In this way, switch 131 provides auseful indication, which preferably is used to stop car 11, and whichindicates the occurence of said type of acceleration force. I

In operation, compensating sheave assembly 17 follows an operatingsequence. When an upward rope shrinkage force or upward accelerationforce is applied to compensating sheave assembly 17 by compensatingropes 16, the following operating sequence occurs:

1. When the upward force is applied to compensating sheave assembly 17by compensating ropes 16, the upward force is transmitted from sheave 20through sheave shaft and frame 21 and springs 61, 62 to block assembly44.

. If the upward force is a rope shrinkage force, which has substantiallyno acceleration rate, block assembly 44 is not accelerated upwardly andinertial mass 101 is not urged downwardly relative thereto. Thus, if theupward force is a rope shrinkage force, the inertial mass 101 does notapply an actuating force urging compensating sheave assembly 17 to griprails 22, 23, and compensating sheave assembly 17 can move upwardlyrelative to rails 22, 23 to automatically relieve the rope shrinkageforce in ropes l6.

. if the upward force is an acceleration force, block assembly 44 isaccelerated upwardly at a substantial acceleration rate thereby causinga downward force on inertial mass 101 and an actuating torque on shaft100. The actuating torque on shaft 100 causes a direct force from catchbar 120 to latch pin tip 124.

4. If the acceleration rate of block assembly 44 equals or exceeds apredetermined acceleration rate, spring 129 compresses and latch pin 121deflects inwardly thereby releasing catch bar 120 to permit an angulardisplacement of shaft 100. This is because the spring rate of spring 129is proportional to the level of the predetermined acceleration rate.

5. Thereafter, the actuating torque is transmitted through shaft 100 andend arms 105, 106 to rollers 45, 46 thereby displacing rollers 45, 46through gaps 91, 92 into engagement with cam surfaces 74, 84.Simultaneously, block assembly 44 and its cam surfaces 74, 84 moveupwardly wedging rollers 45, 46 between surfaces 41, 74 and 42, 84. inthis way, when ropes l6 apply a predetermined acceleration force tosheave unit 17, block assembly 44 is clamped to rails 22, 23, but whenropes 16 apply a lesser acceleration force or a rope shrinkage forcethereto, block assembly 44 is not clamped to rails 22, 23.

in summary, the present invention provides an elevator system having acompensating rope sheave unit, wherein rope stress caused by ropeshrinkage is minimized, wherein the compensating sheave unit is actuatedto fixedly tie down the compensating ropes only when the compensatingropes apply a predetermined acceleration force to the compensatingsheave unit, wherein the compensating sheave unit includes a sheaveframe and a separate brake apparatus connected to the sheave frame and aseparate inertial actuator that is operative to actuate the safety brakeapparatus only upon sensing the predetermined acceleration force, andwherein the compensating sheave unit includes adjusting means forchanging the level of the predetermined acceleration force at which thesafety brake apparatus is actuated.

While the present invention has been described in a preferredembodiment, it will be obvious to those skilled in the art that variousmodifications can be made therein within the scope of the invention. Forexample, one such modification within the scope of the invention isindicated hereafter. Braking members 45, 46 can be a pair of pawlsinstead, which are pivotally mounted on block assembly 44 and whichengage respective tooth recesses in guide rails 22, 23. Also, actuator47 can comprise a linkage instead, which is connected to the pawls forsimultaneous movement thereof, a spring mechanism, which urges the pawlsinto engagement with the tooth recesses, a latching device, whichengages the linkage to restrain movement of the linkage and therebyprevent engagement of the pawls with the tooth recesses, and an inertialmass, which is connected to the latching device for selectivelyreleasing the latching device. With such construction, engagement of thepawls with the tooth recesses is caused when the inertial mass senses apredetermined acceleration rate. In addition, another example of amodification within the scope of the invention is indicated hereafter.Restraining mechanism 102 can comprise spring means instead, whichinterconnects inertial mass 101 and block assembly 44, and can comprisean adjustable connection, which connects one end of the spring means toblock assembly 44. Therefore, it is intended that the invention not belimited to the particular embodiment and arrangement which has beendescribed.

What is claimed is:

1. In an elevator system comprising an elevator car, a counterweight, ahoisting machine including a rotatable traction sheave, hoisting ropesextending from a fastening at the top of said car upwardly over saidsheave and downwardly to a fastening atop said counterweight, atensioning sheave, compensating ropes extending downwardly from afastening at the bottom of said car, under said tensioning sheave andupwardly to a fastening at the bottom of said counterweight, a weightframe connected to said tensioning sheave, guide rails guiding movementof said weight frame and tensioning sheave, a safety block connected tosaid weight frame, a pair of coupling members mounted on said safetyblock and movable relative thereto when actuated to grip said guide railmeans, inertial actuator means including an inertial mass mounted onsaid safety block and movable relative thereto, and connecting meansinterconnecting said inertial actuator means and said coupling members,said inertial actuator including a restraining means, said restrainingmeans being arranged to apply a substantially constant restraining forceto said connecting means for preventing movement of said pair ofcoupling members, said restraining means being operative to remove saidrestraining force from said connecting means for releasing saidconnecting means when the inertial mass and said safety block areaccelerated at a rate equal to or in excess of a predeterminedacceleration rate.

2. An elevator system as claimed in claim 1, wherein said restrainingmeans has adjusting means for changing the amount of said restrainingforce.

3. An elevator system as claimed in claim 2, wherein said connectingmeans includes a shaft supported by said safety block for rotationrelative thereto, and wherein said pair of coupling members and saidinertial mass are eccentrically connected to said shaft.

4. An elevator system as claimed in claim 3, wherein said restrainingmeans includes, a latching mechanism mounted on said safety block, and acatch means mounted on said shaft and arranged to cooperate with saidlatching mechanism.

5. An elevator system as claimed in claim 4, wherein said latchingmechanism includes, a cylinder mounted on said safety block, a latch pindisposed in said cylinder for displacement relative thereto, and anelongate compression spring disposed in said cylinder and arranged tourge said latch pin outwardly from said cylinder for applying arestraining force against said catch means.

6. An elevator system as claimed in claim 5, wherein said cylinderincludes, a fixed portion which engages one end of said compressionspring, and an adjustable portion which engages the other end of saidcompression spring, said adjustable portion being adjustably movablerelative to said fixed portion for changing the spring rate of saidcompression spring.

7. An elevator system as claimed in claim 3, wherein said safety blockhas opposite end portions having respective cam surfaces respectivelyfacing said guide rails, and wherein said coupling members are a pair ofrollers, and wherein said shaft has arm portions respectively connectedto said rollers, said arm portions being arranged to urge said rollersagainst said cam surfaces and said guide rails adjacent thereto whensaid shaft is actuated.

8. An elevator system as claimed in claim 7, wherein said block endportions have recesses respectively receiving said guide rails, eachsaid recess having first and second sidewalls disposed on opposite sidesof the guide rail adjacent thereto, said first sidewalls havingrespective surfaces inclined to the guide rails for forming the camsurfaces.

9. An elevator system as claimed in claim 8, wherein each end portionhas a bearing member disposed between the second sidewall and the guiderail adjacent thereto, and wherein the second sidewall has spring meanssupported therefrom urging the bearing member against the guide rail.

10. An elevator system as claimed in claim 3, wherein said weight frameis connected to said safety block by slidable connecting means, saidslidable connecting means being arranged to permit a limited amount oftravel of said weight frame relative to said safety block.

11. An elevator system as claimed in claim 10, including switch meansmounted on said safety block, said switch means having a tripper portionarranged to engage the weight frame when the weight frame engages thesafety block.

12. A compensating sheave apparatus for an elevator comprising, acompensating sheave, a shaft on which said sheave is journaled, a weightframe journaled on said shaft, fixed guide means constraining movementof said compensating sheave and said weight frame, and a safety deviceconnected to said weight frame and responsive to movement of said frameand compensating sheave at a rate of acceleration in excess of apredetermined rate to fasten said frame and sheave to said fixed guidemeans, wherein said guide means includes a pair of guide rails, and saidsafety device includes a safety block disposed between said guide railsfor cooperation therewith,

said safety block being connected to said weight frame for limitedtravel relative thereto, coupling means mounted on said safety block andmovable relative thereto, said coupling means being operative whenactuated to grip said guide rails, and an inertial actuator having aninertial mass mounted on said safety block and movable relative to saidblock, said inertial actuator being held inoperative to actuate saidcoupling means until said inertial mass senses a rate of acceleration inexcess of said predetermined acceleration rate.

13. A compensating sheave apparatus as claimed in claim 12, wherein saidsafety block has resilient means disposed between said safety block andsaid weight frame, and said safety block has a pair of end portionshaving respective recesses receiving said guide rails, each said recesshaving a sidewall having a cam surface inclined to said guide railadjacent thereto; and wherein said coupling means includes a pair ofrollers respectively disposed in said recesses between the cam surfacesand guide rails; and wherein said actuator includes a shaft rotatablymounted on said safety block and connected to said inertial mass andincludes a restraining mechanism mounted on said safety block forrestraining said shaft, said shaft having respective arm portionsconnected to said inertial mass and to each of said rollers, saidrestraining mechanism including a cylinder mounted on said safety blockand a latch pin disposed in said cylinder and an elongate springdisposed in said cylinder for urging said latch pin into latchingengagement with said shaft, said cylinder having an adjustable wallportion engaging said spring for adjusting the spring rate thereof.

1. In an elevator system comprising an elevator car, a counterweight, ahoisting machine including a rotatable traction sheave, hoisting ropesextending from a fastening at the top of said car upwardly over saidsheave and downwardly to a fastening atop said counterweight, atensioning sheave, compensating ropes extending downwardly from afastening at the bottom of said car, under said tensioning sheave andupwardly to a fastening at the bottom of said counterweight, a weightframe connected to said tensioning sheave, guide rails guiding movementof said weight frame and tensioning sheave, a safety block connected tosaid weight frame, a pair of coupling members mounted on said safetyblock and movable relative thereto when actuated to grip said guide railmeans, inertial actuator Means including an inertial mass mounted onsaid safety block and movable relative thereto, and connecting meansinterconnecting said inertial actuator means and said coupling members,said inertial actuator including a restraining means, said restrainingmeans being arranged to apply a substantially constant restraining forceto said connecting means for preventing movement of said pair ofcoupling members, said restraining means being operative to remove saidrestraining force from said connecting means for releasing saidconnecting means when the inertial mass and said safety block areaccelerated at a rate equal to or in excess of a predeterminedacceleration rate.
 2. An elevator system as claimed in claim 1, whereinsaid restraining means has adjusting means for changing the amount ofsaid restraining force.
 3. An elevator system as claimed in claim 2,wherein said connecting means includes a shaft supported by said safetyblock for rotation relative thereto, and wherein said pair of couplingmembers and said inertial mass are eccentrically connected to saidshaft.
 4. An elevator system as claimed in claim 3, wherein saidrestraining means includes, a latching mechanism mounted on said safetyblock, and a catch means mounted on said shaft and arranged to cooperatewith said latching mechanism.
 5. An elevator system as claimed in claim4, wherein said latching mechanism includes, a cylinder mounted on saidsafety block, a latch pin disposed in said cylinder for displacementrelative thereto, and an elongate compression spring disposed in saidcylinder and arranged to urge said latch pin outwardly from saidcylinder for applying a restraining force against said catch means. 6.An elevator system as claimed in claim 5, wherein said cylinderincludes, a fixed portion which engages one end of said compressionspring, and an adjustable portion which engages the other end of saidcompression spring, said adjustable portion being adjustably movablerelative to said fixed portion for changing the spring rate of saidcompression spring.
 7. An elevator system as claimed in claim 3, whereinsaid safety block has opposite end portions having respective camsurfaces respectively facing said guide rails, and wherein said couplingmembers are a pair of rollers, and wherein said shaft has arm portionsrespectively connected to said rollers, said arm portions being arrangedto urge said rollers against said cam surfaces and said guide railsadjacent thereto when said shaft is actuated.
 8. An elevator system asclaimed in claim 7, wherein said block end portions have recessesrespectively receiving said guide rails, each said recess having firstand second sidewalls disposed on opposite sides of the guide railadjacent thereto, said first sidewalls having respective surfacesinclined to the guide rails for forming the cam surfaces.
 9. An elevatorsystem as claimed in claim 8, wherein each end portion has a bearingmember disposed between the second sidewall and the guide rail adjacentthereto, and wherein the second sidewall has spring means supportedtherefrom urging the bearing member against the guide rail.
 10. Anelevator system as claimed in claim 3, wherein said weight frame isconnected to said safety block by slidable connecting means, saidslidable connecting means being arranged to permit a limited amount oftravel of said weight frame relative to said safety block.
 11. Anelevator system as claimed in claim 10, including switch means mountedon said safety block, said switch means having a tripper portionarranged to engage the weight frame when the weight frame engages thesafety block.
 12. A compensating sheave apparatus for an elevatorcomprising, a compensating sheave, a shaft on which said sheave isjournaled, a weight frame journaled on said shaft, fixed guide meansconstraining movement of said compensating sheave and said weight frame,and a safety device connected to said weight frame and responsive tomovement of said frame and Compensating sheave at a rate of accelerationin excess of a predetermined rate to fasten said frame and sheave tosaid fixed guide means, wherein said guide means includes a pair ofguide rails, and said safety device includes a safety block disposedbetween said guide rails for cooperation therewith, said safety blockbeing connected to said weight frame for limited travel relativethereto, coupling means mounted on said safety block and movablerelative thereto, said coupling means being operative when actuated togrip said guide rails, and an inertial actuator having an inertial massmounted on said safety block and movable relative to said block, saidinertial actuator being held inoperative to actuate said coupling meansuntil said inertial mass senses a rate of acceleration in excess of saidpredetermined acceleration rate.
 13. A compensating sheave apparatus asclaimed in claim 12, wherein said safety block has resilient meansdisposed between said safety block and said weight frame, and saidsafety block has a pair of end portions having respective recessesreceiving said guide rails, each said recess having a sidewall having acam surface inclined to said guide rail adjacent thereto; and whereinsaid coupling means includes a pair of rollers respectively disposed insaid recesses between the cam surfaces and guide rails; and wherein saidactuator includes a shaft rotatably mounted on said safety block andconnected to said inertial mass and includes a restraining mechanismmounted on said safety block for restraining said shaft, said shafthaving respective arm portions connected to said inertial mass and toeach of said rollers, said restraining mechanism including a cylindermounted on said safety block and a latch pin disposed in said cylinderand an elongate spring disposed in said cylinder for urging said latchpin into latching engagement with said shaft, said cylinder having anadjustable wall portion engaging said spring for adjusting the springrate thereof.